This special issue highlights five articles covering several topics in ultrascale data visualization, including extreme-scale production software, ghost-data generation, biomedical-image segmentation and remote viewing, in situ visualization, and display-rich global collaborative cyberinfrastructure. Underlying the different research focuses is a common theme: how to prepare ourselves to address the challenges brought by supercomputers that will soon include one million cores and beyond. Besides presenting new research ideas, the articles in this issue discuss current visualization software's limitations, the major bottleneck in future hardware architectures that will prevent us from developing scalable visualization solutions, the unification of software and hardware to enable remote collaboration, the future trend of biomedical imaging, and the need to create seamless workflows for data generation and analysis.